Ok ... one newbie to another... Yes, if you aerate (Or in extreme cases de-thatch) before you seed, you will increase the likelihood of the seed coming in contact with the soil, as well as the nutrients that will follow seeding. Also, it is popular and in some cases a good idea to fertilize after.

There, now lets see what the pro's have to say... I had to try to answer this one as I think I am somewhat knowledgeable on this one... Somewhat.

This is my typical powerseed job:
Evaluate the lawn, if there is too much competition between the new seedlings and weeds, consider killing the entire lawn and starting fresh. After the lawn is dead, mow short, at the lowest level, like "scalping". It may be a good idea to then dethatch the dead grass to expose more soil (collecting or raking up the dead grass). I like to at this point, if feasible, place some topdressing over the lawn. Aerate at least two passes, one pass in each direction, like a criscross pattern, leaving the plugs to breakdown on their own. Now you are ready to powerseed. Depending on the uses and area you live, determine what type of seed is best for you. On the seed bag, most likely will be a recommended application rate, for both overseeding or a new lawn, use this one. Powerseeding is the process of "injecting" seed into a existing lawn. (there will most likely still be some dead grass that was not removed, this is okay, thats what the powerseeder is for.) The machine has a set of fixed (not free spinning as a dethatcher) blades which follow and bury the seed as it falls from the hopper, usually 1/4 inch into the ground. This is the preferred depth I believe. Use half the remommended rate in each direction, again like a criscross pattern, this ensures a good distribution of the seed. Dont forget to place the starter fert. Some people like to place straw/hay over the lawn at this point, some dont, I have always had good luck doing this step. Now water for at least six times a day for about ten minutes, gradually reducing the number of waterings down , but increasing the amount of time water is being applied. I'm being rushed by the wife now, thats it in a nutshell, hope it helps.... good luck!!